Hybrid bond pad structure

ABSTRACT

In some embodiments, the present disclosure relates to a method of forming a multi-dimensional integrated chip. The method includes forming a first plurality of interconnect layers within a first dielectric structure on a front-side of a first substrate and forming a second plurality of interconnect layers within a second dielectric structure on a front-side of a second substrate. A first redistribution layer coupled to the first plurality of interconnect layers is bonded to a second redistribution layer coupled to the second plurality of interconnect layers along an interface. A recess is formed within a back-side of the second substrate and over the second plurality of interconnect layers. A bond pad is formed within the recess. The bond pad is laterally separated from the first redistribution layer by a non-zero distance.

REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. application Ser. No.15/626,834, filed on Jun. 19, 2017, which is a Continuation of U.S.application Ser. No. 14/750,003, filed on Jun. 25, 2015 (now U.S. Pat.No. 9,704,827, issued on Jul. 11, 2017). The contents of theabove-referenced patent applications are hereby incorporated byreference in their entirety.

BACKGROUND

A multi-dimensional integrated chip is an integrated circuit havingmultiple substrates or die which are vertically stacked onto andelectrically interconnected to one another. By electricallyinterconnecting the stacked substrates or die, the multi-dimensionalintegrated chip acts as a single device, which provides improvedperformance, reduced power consumption, and a reduced footprint overconvention integrated chips. Therefore, multi-dimensional integratedchips provide a path to continue to meet the performance/cost demands ofnext-generation integrated circuits without further lithographicscaling.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 illustrates some embodiments of a stacked integrated chip havinga back-side bond pad.

FIGS. 2A-6 illustrate some alternative embodiments of a stackedintegrated chip having a back-side bond pad.

FIG. 7 illustrates some additional embodiments of a stacked integratedchip image sensor having a back-side bond pad for a back-sideilluminated (BSI) image sensor.

FIG. 8 illustrates some additional embodiments of a back-sideilluminated (BSI) image sensor.

FIG. 9 illustrates a flow diagram of some embodiments of a method offorming a stacked integrated chip having a back-side bond pad.

FIGS. 10A-17 illustrate some embodiments of cross-sectional viewsshowing a method of forming a stacked integrated chip having a back-sidebond pad.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Three-dimensional integrated chips (3DIC) are manufactured by stacking aplurality of integrated chip die on top of one another. The plurality ofintegrated chip die are separately produced by forming one or moremetallization layers within ILD layers overlying separate semiconductorsubstrates. One or more redistribution layers are then formed within theILD layers over the metallization layers and a planarization process(e.g., a chemical mechanical polishing process) is performed to form aplanar surface comprising the redistribution layers and the ILD layer.The planar surfaces of the separate integrated chip die are then broughttogether so that the redistribution layers of the separate integratedchip die abut. A bond pad is subsequently produced within a recessvertically extending through an upper substrate to an underlyingmetallization layer, so as to provide an electrical connection betweenthe bond pad and the multi-dimensional integrated chip.

When the planarization process is performed on the separate integratedchip die, an upper surface of the redistribution layer may ‘dish’ toform a concave surface that drops below the surrounding ILD layer. Whenthe planar surfaces of two integrated chip die are subsequently broughttogether, the concave surfaces come together to form one or more bubblesat the interface of the two integrated chip die. The bubblesstructurally weaken a region below the bond pad, such that if a forceused to form a bonding structure onto the bond pad is too large, thestructure underlying the bond pad may crack and damage themulti-dimensional integrated chip.

The present disclosure relates to a multi-dimensional integrated chiphaving a redistribution layer vertically extending between integratedchip die, which is laterally offset from a back-side bond pad, and acorresponding method of formation. In some embodiments, themulti-dimensional integrated chip has a first integrated chip die with afirst plurality of metal interconnect layers disposed within a firstinter-level dielectric (ILD) layer arranged onto a front-side of a firstsemiconductor substrate. The multi-dimensional integrated chip also hasa second integrated chip die with a second plurality of metalinterconnect layers disposed within a second ILD layer abutting thefirst ILD layer. A bond pad is disposed within a recess extendingthrough the second semiconductor substrate. A redistribution layervertically extends between the first plurality of metal interconnectlayers and the second plurality of metal interconnect layers at aposition that is laterally offset from the bond pad. Since theredistribution layer is laterally offset from the bond pad, a regionunderlying the bond pad is devoid of bubbles along the interface betweenthe first integrated chip die and the second integrated chip die.Without bubbles underlying the bond pad, the structural integrity of thebond pad is increased, thereby reducing cracking and damage to themulti-dimensional integrated chip.

FIG. 1 illustrates some embodiments of a stacked integrated chip 100having a back-side bond pad.

The stacked integrated chip 100 comprises a first integrated chip die102 and a second integrated chip die 110. The first integrated chip die102 comprises a first back-end-of-the-line (BEOL) metallization stack108 arranged onto a front-side 104 a of a first semiconductor substrate104. The first BEOL metallization stack 108 comprises one or more metalinterconnect layers arranged within a first inter-layer dielectric (ILD)layer 106 comprising one or more ILD materials (e.g., a low-k dielectricmaterial, silicon dioxide, etc.). In some embodiments, the firstsemiconductor substrate 104 may comprise a device region 105 having aplurality of semiconductor devices (e.g., transistor devices,capacitors, inductors, etc.) and/or MEMs devices.

The second integrated chip die 110 comprises a secondback-end-of-the-line (BEOL) metallization stack 116 arranged onto afront-side 112 a of a second semiconductor substrate 112. The secondBEOL metallization stack 116 has one or more metal interconnect layersarranged within a second ILD layer 114 comprising one or more ILDmaterials. In some embodiments, the second semiconductor substrate 112may comprise integrated chip devices, imaging devices, or MEMs devices,for example. The first integrated chip die 102 is vertically stackedonto the second integrated chip die 110 in a face-to-face (F2F)configuration, such that the first ILD layer 106 abuts the second ILDlayer 114.

A bond pad 120, which is in electrical contact with the second BEOLmetallization stack 116, is arranged within a recess 122 that extendsthrough a portion of the second semiconductor substrate 112 (e.g., fromthe front-side 112 a of the substrate to a back-side 112 b of thesubstrate). The bond pad 120 comprises a conductive material (e.g., ametal such as aluminum) and has an upper surface that is exposed by therecess 122. The bond pad 120 is configured to provide an electricalconnection between the stacked integrated chip 100 and an externaldevice. For example, a solder bump (not shown) may be formed onto thebond pad 120 to connect the bond pad 120 to an external I/O pin of anintegrated chip package. In some embodiments, the bond pad 120 maycomprise a slotted bond pad. The slotted bond pad comprises protrusions120 b extending vertically outward from a lower surface of a base region120 a to an underlying metal interconnect layer within the second BEOLmetallization stack 116. In some embodiments, pad openings 124 arearranged within an upper surface of the base region 120 a. The padopenings 124 may vertically extend to within the protrusions 120 b.

A first metal routing layer 109 disposed within the first BEOLmetallization stack 108 extends laterally outward from a bond pad area126 underlying the bond pad 120. In some embodiments, within the bondpad area 126 the first BEOL metallization stack 108 and/or the secondBEOL metallization stack 116 may be a solid bond pad having metal viasarranged between one or more solid metal wire layers (e.g., a solidintermediate metal wire layer and/or a solid top metal wire layer). Inother embodiments, within the bond pad area 126 the first BEOLmetallization stack 108 and/or the second BEOL metallization stack 116may be a slotted bond pad having metal vias arranged between one or moreslotted metal wire layers (e.g., a slotted intermediate metal wire layerand/or a slotted top metal wire layer). In some embodiments, the firstmetal routing layer 109 laterally extends beyond an adjacent metal wirelayer. Similarly, a second metal routing layer 117 disposed within thesecond BEOL metallization stack 116 laterally extends outward from thebond pad area 126 in a same direction as the first metal routing layer109.

The first metal routing layer 109 is electrically connected to thesecond metal routing layer 117 by way of a redistribution structure 118that is laterally offset from the bond pad 120. The redistributionstructure 118 comprises a conductive material that vertically extendsfrom within the first ILD layer 106 to within the second ILD layer 114.In some embodiments, the redistribution structure 118 may comprisecopper and/or aluminum, for example. Since the redistribution structure118 is laterally offset from the bond pad 120, the bond pad area 126 isdevoid of routing between the first BEOL metallization stack 108 and thesecond BEOL metallization stack 116.

In some embodiments, the redistribution structure 118 may comprise abubble or void 119 arranged along an interface 128 between the firstintegrated chip die 102 and the second integrated chip die 110. However,since the redistribution structure 118 is laterally offset from the bondpad area 126, the bond pad area 126 is devoid of void along theinterface between the first integrated chip die 102 and the secondintegrated chip die 110. Without voids underlying the bond pad 120, abonding structure (e.g., a wirebond ball) can be formed onto the bondpad 120 without damaging the underlying structure of stacked integratedchip 100.

FIG. 2A illustrates a cross-sectional view of some additionalembodiments of a stacked integrated chip 200 having a back-side bondpad.

The stacked integrated chip 200 comprises a first integrated chip die102, and a second integrated chip die 201 that is vertically stackedonto the first integrated chip die 102 in a F2F configuration. The firstintegrated chip die 102 comprises a first BEOL metallization stack 204disposed within a first ILD layer 202 arranged onto a front-side of afirst semiconductor substrate 104. The first BEOL metallization stack204 includes a first plurality of metal interconnect layers comprisingalternating layers of metal wires 206 a (configured to provide lateralconnections) and metal vias 208 a (configured to provide verticalconnections). The first plurality of metal interconnect layers furtherinclude a first upper metal wire layer 210 (e.g., a top metal wire layerwithin the first BEOL metallization stack 208) that laterally extends toa position outside of a bond pad area 126 (e.g., to a position that islaterally offset from slotted bond pad 226).

The second integrated chip die 201 comprises a second BEOL metallizationstack 214 disposed within a second ILD layer 212 arranged onto afront-side of a second semiconductor substrate 224. The second BEOLmetallization stack 214 includes a second plurality of metalinterconnect layers comprising a bond pad layer 216 and a second uppermetal wire layer 218 (e.g., a top metal wire layer within the secondBEOL metallization stack 214) vertically separated by one or more metalwires 206 b and metal vias 208 b. In some embodiments, the bond padlayer 216 may comprise a first metal interconnect layer (e.g., a“lowest” metal wire layer within the second BEOL metallization stack214). The second upper metal wire layer 218 laterally extends to aposition outside of a bond pad area 126 (e.g., to a position that islaterally offset from slotted bond pad 226).

The first and second plurality of metal interconnect layers are stackedonto one another in a bond pad configuration, which has the metal wires206 and metal vias 208 stacked vertically onto one another to providestructural stability for the overlying slotted bond pad 226. The stackedmetal vias 208 are laterally aligned between different metal viaslayers. In some embodiments, the metal wires 206 and metal vias 208 maybe arranged in a periodic pattern. In some embodiments, the first and/orsecond plurality of metal interconnect layers may have a slottedstructure. In such embodiments, the metal wires 206 b and metal vias 208b within the second plurality of metal interconnect layers may have aplurality of column structures laterally separated from one another andvertically extending between the upper metal wire layer 218 and the bondpad layer 216. In other embodiments, the first and/or second pluralityof metal interconnect layers may have metal wires with a solidstructure. In such embodiments, the metal wires 206 b between the uppermetal wire layer 218 and the bond pad layer 216 may comprise a solidstructure laterally extending between a plurality of metal vias 208 b ona same metal via layer. In some embodiments, the first upper metal wirelayer 210 and the second upper metal wire layer 218 extend laterallypast the other plurality of metal interconnect layers in the bond padconfiguration.

In some embodiments, the first ILD layer 202 and the second ILD layer212 may comprise one or more of a low-k dielectric (i.e., a dielectricwith a dielectric constant less than about 3.9), an ultra low-kdielectric, or an oxide. In some embodiments, the first and secondplurality of metal interconnect layers may comprise as aluminum, copper,tungsten, or some other metal.

A redistribution structure 220 configured to provide an electricalconnection between the first BEOL metallization stack 204 and the secondBEOL metallization stack 214 is located at a position that is laterallyoffset from the bond pad area 126 (e.g., a position that is laterallyoffset from slotted bond pad 226). The redistribution structure 220comprises a first redistribution layer 220 a and a second redistributionlayer 220 b. The first redistribution layer 220 a abuts the first uppermetal wire layer 210 at a position laterally outside of a bond pad area126. The second redistribution layer 220 b abuts the second upper metalwire layer 218 at a position laterally outside of a bond pad area 126.In some embodiments, the first redistribution layer 220 a and the secondredistribution layer 220 b have concave surfaces that meet to form abubble 222 at an interface between the stacked integrated chip die.

A recess 232 is arranged in a back-side of the second semiconductorsubstrate 224. A buffer layer 228 is disposed along interior surfaces ofthe recess 232. In some embodiments, the buffer layer 228 is confined tothe recess 232. In other embodiments, the buffer layer 228 may extendoutward from the recess 232. In some embodiments, the buffer layer 228may comprise a single or multi-layer dielectric film including an oxide(e.g., silicon dioxide), a nitride (e.g., silicon nitride), and/or ahigh k dielectric (i.e., having a dielectric constant greater than about3.9).

A slotted bond pad 226 is disposed within the recess 232 at a positionoverlying the buffer layer 228. The slotted bond pad 226 comprisesprotrusions 226 b vertically extending outward from a base region 226 a,through the buffer layer 228, to the bond pad layer 216. In variousembodiments, the slotted bond pad 226 may comprise a conductivematerial, such as copper and/or aluminum, for example. A dielectriclayer 230 is arranged within the recess 232 at a location over theslotted bond pad 226. In some embodiments, the dielectric layer 230 maycomprise an oxide, such as silicon dioxide. An opening 234 verticallyextends through the dielectric layer 230 to expose an upper surface ofthe slotted bond pad 226.

FIG. 2B illustrates a top-view 236 of some embodiments of the stackedintegrated chip 200 shown along line A-A′ of FIG. 2A.

As shown in top-view 236, the second upper metal wire layer 218 maycomprise a solid bond pad configuration having a metal plate 218 awithin the bond pad area 126 underlying the slotted bond pad (e.g.,element 226 of FIG. 2A). Extensions 218 b protrude outward from themetal plate 218 a to a redistribution landing area 218 c configured tomake contact with a plurality of redistribution structures 220. In someembodiments, the metal plate 218 a and the redistribution landing area218 c continuously extend in a first direction 238 along multipleextensions 218 b extending along a second direction 240 and separatedfrom one another in the first direction 238.

It will be appreciated that top-view 236 is a non-limiting example ofthe second upper metal wire layer 218 for a solid bond padconfiguration. In other embodiments, the second upper metal wire layer218 may have an alternative structure, such as for example a non-solidstructure for a slotted bond pad configuration.

FIG. 3 illustrates some alternative embodiments of a stacked integratedchip 300 having a back-side bond pad.

The stacked integrated chip 300 comprises a first integrated chip die102, and a second integrated chip die 302 vertically stacked onto thefirst integrated chip die 102. The first integrated chip die 102comprises a first BEOL metallization stack 204 having a first uppermetal wire layer 210 that horizontally extends to a position that islaterally offset from a slotted bond pad 226. The second integrated chipdie 302 comprises a second BEOL metallization stack 304 comprising anintermediate metal interconnect layer 306 vertically arranged between abond pad layer 216 (that abuts the slotted bond pad 226) and a secondupper metal wire layer 218. The intermediate metal interconnect layer306 horizontally extends to a position laterally offset from the slottedbond pad 226.

A redistribution structure 220 forms an electrical connection extendingbetween the first upper metal wire layer 210 and the intermediate metalinterconnect layer 306 at a position that is laterally offset from theslotted bond pad 226. The redistribution structure 220 comprises a firstredistribution layer 220 a abutting the first upper metal wire layer210, and a second redistribution layer 220 b connected to theintermediate metal interconnect layer 306 by way of one or moreconnecting metal interconnect layers 308.

FIG. 4 illustrates some alternative embodiments of a stacked integratedchip 400 having a back-side bond pad.

The stacked integrated chip 400 comprises a first integrated chip die402, and a second integrated chip die 302 vertically stacked onto thefirst integrated chip die 402. The first integrated chip die 402comprises a first BEOL metallization stack 404 having a firstintermediate metal interconnect layer 406 vertically arranged between afirst semiconductor substrate 104 and a first upper metal layer 210. Thefirst intermediate metal interconnect layer 406 horizontally extends toa position that is laterally offset from slotted bond pad 226. Thesecond integrated chip die 302 comprises a second BEOL metallizationstack 304 comprising a second intermediate metal interconnect layer 306vertically arranged between a bond pad layer 216 and a second uppermetal wire layer 218. The second intermediate metal interconnect layer306 horizontally extends to a position that is laterally offset from theslotted bond pad 226.

A redistribution structure 220 forms an electrical connection extendingbetween first intermediate metal interconnect layer 406 and the secondintermediate metal interconnect layer 306 at a position that islaterally offset from the slotted bond pad 226. The redistributionstructure 220 comprises a first redistribution layer 220 a connected tothe first intermediate metal interconnect layer 406 by way of one ormore first connecting metal interconnect layers 408, and a secondredistribution layer 220 b connected to the second intermediate metalinterconnect layer 306 by way of one or more second connecting metalinterconnect layers 308.

FIG. 5 illustrates some alternative embodiments of a stacked integratedchip 500 having a back-side bond pad.

The stacked integrated chip 500 comprises a first integrated chip die402, and a second integrated chip die 502 vertically stacked onto thefirst integrated chip die 402. The second integrated chip die 502 has anupper metal wire layer 504 comprising a slotted structure. The slottedstructure comprises a plurality of segments 504 a-504 n that arelaterally separated from one another. The plurality of segments 504a-504 n are respectively connected to adjacent metal vias 208, whichcouple one or more of the plurality of segments 504 a-504 n to a secondintermediate metal interconnect layer 306 coupled to a redistributionstructure 220.

FIG. 6 illustrates a cross-sectional view of some alternativeembodiments of a stacked integrated chip 600 having a back-side bondpad.

The stacked integrated chip 600 comprises a first integrated chip die602, and a second integrated chip die 302 vertically stacked onto thefirst integrated chip die 602. The second integrated chip die 302 has asecond plurality of metal interconnect layers stacked onto one anotherin a bond pad configuration (e.g., in a slotted or solid padconfiguration), which has the metal wires and metal vias stackedvertically onto one another to provide structural stability for anoverlying slotted bond pad 226. The first integrated chip die 602comprises a plurality of metal wire layers 604 and metal via layers 606configured to provide routing for integrated circuit logic elements. Theplurality of metal wire layers 604 and metal via layers 606 are notarranged in a bond pad configuration. For example, the metal via layers606 (e.g., a first via layer and an overlying second via layer) are notaligned in a lateral direction within a bond pad area 126 underlying theslotted bond pad 226.

FIG. 7 illustrates some additional embodiments of a back sideillumination (BSI) image sensor 700 having a back-side bond pad.

The BSI image sensor 700 comprises a first integrated chip die 102 and asecond integrated chip die 702, which is vertically stacked onto thefirst integrated chip die 102. The second integrated chip die 702comprises a second semiconductor substrate 704 and an isolation region716. The second semiconductor substrate 704 and the isolation region 716both abut an upper surface of the second ILD layer 212, and theisolation region 716 extends vertically therefrom into the secondsemiconductor substrate 704. In some embodiments, the isolation region716 may comprise an oxide or an implant isolation region.

A recess 714 is arranged within the second semiconductor substrate 704.The recess 714 comprises substantially vertical sidewalls. A slottedbond pad 226 is arranged within the recess at a location overlying abuffer layer 706. A dielectric layer may be disposed within the recess714 over the slotted bond pad 226, and a passivation layer 710 may bearranged over the dielectric layer 708. The passivation layer 710extends along an upper surface of the second semiconductor substrate 704and the dielectric layer 708. In various embodiments, the passivationlayer 710 may comprise a single or multilayer dielectric film includingone or more layers of oxide, nitride, and high-k dielectric. A metalconnect layer 712 is arranged over the passivation layer 710 and extendsinto the recess 714 to a position in contact with a slotted bond pad226. In various embodiments, the metal connect layer 712 may comprisecopper or aluminum.

FIG. 8 illustrates a cross-sectional view of some embodiments of aback-side illuminated (BSI) image sensor 800.

The BSI image sensor 800 includes a first integrated chip die 102 and asecond integrated chip die 802. The second integrated chip die 802comprises a sensing region 804 and an interconnect region 806. Thesensing region 804 is configured to sense incident radiation (e.g.,visible light). The interconnect region 806 laterally surrounds thesensing region 804 and comprises bond pads 120 that are configured toconnect the BSI image sensor 800 to external devices. The secondintegrated chip die 802 comprises a second semiconductor substrate 808having a front-side 808 a abutting a second ILD layer 212. An array ofpixel sensors 818 are arranged within the front-side 808 a of the secondsemiconductor substrate 808 in the sensing region 804. The array ofpixel sensors 818 comprises a plurality of pixel sensors 820. In variousembodiments, the plurality of pixel sensors 820 may comprisephotodetectors and/or photodiodes.

A passivation layer 710 is arranged along a back-side 808 b of thesecond semiconductor substrate 808. In some embodiments, a metal connectlayer 712 is arranged over the passivation layer 710. An array of colorfilters comprising a plurality of color filters 810-814 is buried in thepassivation layer 710, within the sensing region 804. Typically, theplurality of color filters 810-814 have planar upper surfaces that areapproximately co-planar with an upper surface of the passivation layer710. The plurality of color filters 810-814 are configured to transmitassigned colors or wavelengths of radiation to the corresponding pixelsensors 820. In some embodiments, the plurality of color filters 810-814include blue color filters 810, red color filters 812, and green colorfilters 814. Micro-lenses 816 are arranged over the plurality of colorfilters 810-814. The micro-lenses 816 may have centers aligned withcenters of the plurality of color filters 810-814. The micro-lenses 816are configured to focus incident radiation towards the array of pixelsensors 818 and/or the plurality of color filters 810-814. In someembodiments, the micro-lenses 816 have convex upper surfaces.

FIG. 9 illustrates a flow diagram of some embodiments of a method 900 ofa forming a stacked integrated chip having a back-side bond pad.

While the disclosed method 900 is illustrated and described herein as aseries of acts or events, it will be appreciated that the illustratedordering of such acts or events are not to be interpreted in a limitingsense. For example, some acts may occur in different orders and/orconcurrently with other acts or events apart from those illustratedand/or described herein. In addition, not all illustrated acts may berequired to implement one or more aspects or embodiments of thedescription herein. Further, one or more of the acts depicted herein maybe carried out in one or more separate acts and/or phases.

At 902, a first integrated chip die is formed having a firstback-end-of-the-line (BEOL) metallization stack arranged within a firstILD layer overlying a first semiconductor substrate. In someembodiments, the first integrated chip die may be formed according toacts 904-910.

At 904, a plurality of semiconductor devices are formed within the firstsemiconductor substrate.

At 906, a first plurality of metal interconnect layers are formed withinthe first ILD layer disposed over the first semiconductor substrate. Thefirst plurality of metal interconnect layers comprise a first metalrouting layer extending laterally beyond a bond pad area in which a bondpad is subsequently formed.

At 908, a first redistribution layer is formed in contact with the firstmetal routing layer at a position laterally offset from the bond padarea.

At 910, a first planarization process is performed to form a firstplanar interface comprising the first ILD layer and the firstredistribution layer.

At 912, a second integrated chip die is formed having a second BEOLmetallization stack arranged within a second ILD layer overlying asecond semiconductor substrate. In some embodiments, the secondintegrated chip die may be formed according to acts 914-920.

At 914, an isolation region is formed within the second semiconductorsubstrate.

At 916, a second plurality of metal interconnect layers are formedwithin the second ILD layer disposed over the second semiconductorsubstrate. The second plurality of metal interconnect layers comprise abond pad layer and a second metal routing layer extending laterallybeyond the bond pad area.

At 918, a second redistribution layer is formed in contact with thesecond metal routing layer at a position laterally offset from the bondpad layer.

At 920, a second planarization process is performed to form a secondplanar interface comprising the second ILD layer and the secondredistribution layer.

At 922, the first integrated chip die is bonded to the second integratedchip die in a face to face (F2F) configuration, so that the first andsecond redistribution layers abut one another at an interface comprisingthe first and second ILD layers.

At 924, a recess is formed within the second semiconductor substrate.The recess extends through a portion of the second semiconductorsubstrate.

At 926, a bond pad is formed within the recess. The bond pad verticallyextends to the bond pad connection layer within the second BEOLmetallization stack. In some embodiments, the bond pad may comprise aslotted bond pad.

At 928, a dielectric layer is formed within the recess at a positionoverlying the slotted bond pad.

At 930, a passivation layer is formed over the dielectric layer. Thepassivation layer has an opening that vertically extends through thepassivation layer to the underlying bond pad.

At 932, a metal connect layer is formed onto the passivation layer andwithin the opening.

FIGS. 10A-17 illustrate some embodiments of cross-sectional viewsshowing a method of a forming a stacked integrated chip having aback-side bond pad. Although FIGS. 10A-17 are described in relation tomethod 900, it will be appreciated that the structures disclosed inFIGS. 10A-17 are not limited to such a method, but instead may standalone as structures independent of the method.

FIGS. 10A-10C illustrate some embodiments of cross-sectional views, 1000a-1000 c, of an integrated chip corresponding to act 902.

As shown in cross-sectional view 1000 a, a plurality of semiconductordevices are formed within a device region 105 of a first semiconductorsubstrate 104. The first semiconductor substrate 104 may comprise anytype of semiconductor body (e.g., silicon/CMOS bulk, SiGe, SOI, etc.)such as a semiconductor wafer or one or more die on a wafer, as well asany other type of semiconductor and/or epitaxial layers formed thereonand/or otherwise associated therewith. The semiconductor devices maycomprise active (e.g., MOSFETs) and/or passive devices (e.g., capacitor,inductor, resistor, etc.)

As shown in cross-sectional view 1000 b, a first plurality of metalinterconnect layers 1002 are formed within a first ILD layer 202disposed over the first semiconductor substrate 104. The first pluralityof metal interconnect layers 1002 may be formed by etching the first ILDlayer 202 to form openings. The openings are then filled with aconductive material (e.g., tungsten, copper, aluminum, etc.) to form ametal wire 206 and/or a metal via 208. In some embodiments, the firstplurality of metal interconnect layers 1002 may be disposed in a bondpad configuration.

As shown in cross-sectional view 1000 c, a first metal routing layer1004 is formed extending outward from a first BEOL metallization stack204 to a position laterally offset from a bonding area in which a bondpad is subsequently formed. The first metal routing layer 1004 may beformed by etching the first ILD layer 202 to form an opening, which issubsequently filled with a conductive material (e.g., copper, aluminum,etc.).

A first redistribution layer 220 a is formed over the first metalrouting layer 1004. The first redistribution layer 220 a may be formedby etching the first ILD layer 202 to form an opening that is laterallyoffset from a bond pad area in which a bond pad is subsequently formed.The opening is subsequently filled with a conductive material (e.g.,copper, aluminum, etc.). A first planarization process is then performedto form a first planar interface 1006 comprising the first ILD layer 202and the first redistribution layer 220 a. In some embodiments, the firstplanarization process may cause an upper surface of the firstredistribution layer 220 a to dish, giving the upper surface a concavecurvature.

FIGS. 11A-11C illustrate some embodiments of cross-sectional views, 1100a-1100 c, of an integrated chip corresponding to act 910.

As shown in cross-sectional view 1100 a, an isolation region 1102 isformed within a second semiconductor substrate 224. The isolation region1102 is arranged within a front-side 224 a of the second semiconductorsubstrate 224. In some embodiments, the isolation region 1102 is formedby way of a thermal oxidation process. The second semiconductorsubstrate 224 may comprise any type of semiconductor body (e.g.,silicon/CMOS bulk, SiGe, SOI, etc.) such as a semiconductor wafer or oneor more die on a wafer, as well as any other type of semiconductorand/or epitaxial layers formed thereon and/or otherwise associatedtherewith.

As shown in cross-sectional view 1100 b, a second plurality of metalinterconnect layers 1104 are formed within a second ILD layer 212disposed over the first semiconductor substrate. The second plurality ofmetal interconnect layers 1104 may be formed by etching the second ILDlayer 212 to form openings. The openings are then filled with aconductive material (e.g., tungsten, copper, aluminum, etc.) to form ametal wire 206 and/or a metal via 208. In some embodiments, the secondplurality of metal interconnect layers 1104 may be disposed in a bondpad configuration.

As shown in cross-sectional view 1100 c, a second metal routing layer1106 is formed extending outward from the second BEOL metallizationstack 214 to a position laterally offset from the bonding area in whicha bond pad is subsequently formed. The second metal routing layer 1106may be formed by etching the second ILD layer 212 to form an opening.The opening is then filled with a conductive material (e.g., copper,aluminum, etc).

A second redistribution layer 220 b is formed over the second metalrouting layer 1106. The second redistribution layer 220 b may be formedby etching the second ILD layer 212 to form an opening that is laterallyoffset from the bond pad area. The opening is subsequently filled with aconductive material (e.g., copper, aluminum, etc.). A secondplanarization process is then performed to form a second planarinterface 1108 comprising the second ILD layer 212 and the secondredistribution layer 220 b. In some embodiments, the secondplanarization process may cause an upper surface of the secondredistribution layer 220 b to dish, giving the upper surface a concavecurvature.

FIG. 12 illustrates some embodiments of a cross-sectional view 1200 ofan integrated chip corresponding to act 922.

As shown in cross-sectional view 1200, the first integrated chip die 102is bonded to the second integrated chip die 201 in a face-to-face (F2F)configuration. In some embodiments, the bonding may comprise bump-lesscopper to copper bonding at the redistribution layers, 220 a and 220 b.In other embodiments, the bonding may comprise fusion bonding. In someembodiments, a bubble 222 may form between the first redistributionlayer 220 a and the second redistribution layer 220 b due to dishingcaused by the first and second planarization processes. The bubble 222forms at a location that is laterally offset from a bond pad area inwhich a bond pad is subsequently formed. In some embodiments, the secondsemiconductor substrate 224 may be thinned after bonding.

FIG. 13 illustrates some embodiments of a cross-sectional view 1300 ofan integrated chip corresponding to act 924.

As shown in cross-sectional view 1300, a back-side 224 b of the secondsemiconductor substrate 224 is selectively exposed to a first etchant1302. The first etchant 1302 is configured to remove a portion of thesecond semiconductor substrate 224. In some embodiments, due to overetching, the isolation region 1102 may be eroded by the first etchant1302. The first etchant 1302 forms a recess 232 in the secondsemiconductor substrate 224 overlying the bond pad layer 216 andvertically extending to the isolation region 1102. In some embodiments,the recess 232 extends laterally around an array of pixel sensors (notshown). In some embodiments, the second semiconductor substrate 224 maybe selectively masked prior to exposure to the first etchant 1302 by amasking layer 1304 (e.g., a photoresist layer). In various embodiments,the first etchant 1302 may comprise a dry etchant have an etchingchemistry comprising a fluorine species (e.g., CF₄, CHF₃, C₄F₈, etc.) ora wet etchant (e.g., hydroflouric acid (HF)).

FIGS. 14A-14B illustrate some embodiments of cross-sectional views, 1400a and 1400 b, of an integrated chip corresponding to act 926.

As shown in cross-sectional view 1400 a, a buffer layer 1402 is formedover the second semiconductor substrate 224 and lining the recess 232.The buffer layer 1402 may be formed using vapor deposition (e.g.,chemical vapor deposition (CVD)), thermal oxidation, spin coating, orany other suitable deposition technique. In some embodiments, the bufferlayer 1402 may comprise an oxide, such as silicon dioxide.

The workpiece is subsequently exposed to a second etchant 1404. Thesecond etchant 1404 removes portions of the buffer layer 1402, theisolation region 716, and the second ILD layer 212, resulting intrenches 1408 overlying the bond pad layer 216. In some embodiments, theworkpiece may be selectively masked prior to exposure to the secondetchant 1404 by a masking layer 1406 (e.g., a photoresist layer). Invarious embodiments, the second etchant 1404 may comprise a dry etchanthave an etching chemistry comprising a fluorine species (e.g., CF₄,CHF₃, C₄F₈, etc.) or a wet etchant (e.g., hydroflouric acid (HF)).

As shown in cross-sectional view 1400 b, a slotted bond pad 226 isformed over the buffer layer 1402. The slotted bond pad 226 comprisesprotrusions 226 b extending within the trenches 1408 to a position inelectrical contact with the underlying bond pad layer 216. In someembodiments, the slotted bond pad 226 may be formed by forming a padlayer over the buffer layer 1402. The pad layer may comprise a metal,such as aluminum copper, copper, aluminum, or some other metal. The padlayer is subsequently etched to form the slotted bond pad 226. Theetchant may further form pad openings 124 extending vertically into anupper surface of the pad at a location overlying the protrusions 226 b.

FIG. 15 illustrates some embodiments of a cross-sectional view 1500 ofan integrated chip corresponding to act 928.

As shown in cross-sectional view 1500, a dielectric layer 1502 is formedwithin the recess 232 at a position overlying the slotted bond pad 226and the buffer layer 228. In various embodiments, the dielectric layer1502 may be formed using vapor deposition, thermal oxidation, spincoating, or any other suitable deposition technique. In variousembodiments, the dielectric layer 1502 may comprise an oxide, such assilicon dioxide, or some other dielectric. In some embodiments, achemical mechanical polishing (CMP) process may be performed afterdeposition of the dielectric layer 230.

FIG. 16 illustrates some embodiments of a cross-sectional view 1700 ofan integrated chip corresponding to act 930.

As shown in cross-sectional view 1600, a passivation layer 710 is formedover the second semiconductor substrate 224 and the dielectric layer230. The passivation layer 710 may comprise a single or multilayerdielectric film having one or more layers of oxide, nitride, and/or ahigh-k dielectric. The one or more layers may be formed by sequentiallydepositing the layers using vapor deposition, thermal oxidation, spincoating, or any other suitable deposition technique. After deposition,the passivation layer 710 and the dielectric layer 230 may besubsequently etched to form an opening 1602 that extends to theunderlying slotted bond pad 226.

FIG. 17 illustrates some embodiments of a cross-sectional view 1700 ofan integrated chip corresponding to act 932.

As shown in cross-sectional view 1700, a metal connect layer 712 isformed over the passivation layer 710 and within the opening 1602. Invarious embodiments, the metal connect layer 712 may comprise a metal,such as copper or aluminum copper. In various embodiments, the metalconnect layer 712 may be formed using, for example, vapor deposition,thermal oxidation, spin coating, or any other suitable depositiontechnique.

Therefore, the present disclosure relates to a multi-dimensionalintegrated chip having a redistribution layer vertically extendingbetween integrated chip die, which is laterally offset from a back-sidebond pad.

In some embodiments, the present disclosure relates to amulti-dimensional integrated chip. The multi-dimensional integrated chipcomprises a first integrated chip die comprising a first plurality ofmetal interconnect layers arranged within a first inter-level dielectric(ILD) layer disposed onto a front-side of a first semiconductorsubstrate, and a second integrated chip die comprising a secondplurality of metal interconnect layers arranged within a second ILDlayer disposed onto a front-side of a second semiconductor substrate,wherein the first ILD layer abuts the second ILD layer. Themulti-dimensional integrated chip further comprises a bond pad disposedwithin a recess extending through the second semiconductor substrate,and a redistribution structure vertically extending between one of thefirst plurality of metal interconnect layers and one of the secondplurality of metal interconnect layers at a position that is laterallyoffset from the bond pad.

In other embodiments, the present disclosure relates to amulti-dimensional integrated chip. The multi-dimensional integrated chipcomprises a first integrated chip die comprising a first inter-leveldielectric (ILD) layer disposed onto a front-side of a firstsemiconductor substrate and surrounding a first plurality of metalinterconnect layers comprising a first metal routing layer. Themulti-dimensional integrated chip further comprises a second integratedchip die comprising a second ILD layer disposed onto a front-side of asecond semiconductor substrate and surrounding a second plurality ofmetal interconnect layers comprising a bond pad layer verticallyseparated by one or more metal vias or metal wires from a second metalrouting layer. The multi-dimensional integrated chip further comprises aslotted bond pad disposed within a recess extending through the secondsemiconductor substrate and having protrusions in contact with the bondpad layer. The multi-dimensional integrated chip further comprises aredistribution structure vertically extending between the first metalrouting layer and the second metal routing layer at a position that islaterally offset from the slotted bond pad, wherein a bond pad areaextending below the slotted bond pad is devoid of redistributionstructures extending between the first metal routing layer and thesecond metal routing layer.

In yet other embodiments, the present disclosure relates to a method offorming a multi-dimensional integrated chip. The method comprisesforming a first integrated chip die having a first plurality of metalinterconnect layers arranged within a first inter-level dielectric (ILD)layer disposed on a front-side of a first semiconductor substrate, andforming a second integrated chip die having a second plurality of metalinterconnect layers arranged within a second ILD layer disposed on afront-side of a second semiconductor substrate. The method furthercomprises bonding the first integrated chip die to the second integratedchip die so that a first redistribution layer coupled to the firstplurality of metal interconnect layers abuts a second redistributionlayer coupled to the second plurality of metal interconnect layers at aninterface between the first ILD layer and the second ILD layer. Themethod further comprises forming a recess within a back-side of thesecond semiconductor substrate, and forming a slotted bond pad withinthe recess, wherein the slotted bond pad electrically contacts thesecond plurality of metal interconnect layers.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method of forming a multi-dimensionalintegrated chip, comprising: forming a first plurality of interconnectlayers within a first dielectric structure on a first substrate; forminga second plurality of interconnect layers within a second dielectricstructure on a second substrate; bonding a first connector coupled tothe first plurality of interconnect layers to a second connector coupledto the second plurality of interconnect layers along an interface;etching the second substrate to form sidewalls defining a recess withina back-side of the second substrate and over the second plurality ofinterconnect layers, wherein the recess extends from the back-side ofthe second substrate to the second plurality of interconnect layers, andwherein the second substrate is etched after the first connector isbonded to the second connector; and forming a bond pad within therecess, wherein the bond pad is laterally separated from the firstconnector by a non-zero distance.
 2. The method of claim 1, wherein thebond pad contacts a first conductive wire of the second plurality ofinterconnect layers, the first conductive wire is vertically separatedfrom the first plurality of interconnect layers by one or moreadditional conductive wires of the second plurality of interconnectlayers.
 3. The method of claim 1, wherein a line that vertically extendsthrough the first substrate and the second substrate is arrangedlaterally between outermost sidewalls of the bond pad and outermostsidewalls of the first connector.
 4. The method of claim 1, furthercomprising: forming an image sensing element within the second substrateat a position that is laterally separated from the bond pad.
 5. Themethod of claim 4, wherein the image sensing element is configured toreceive incident radiation that enters into the second substrate at asurface of the second substrate facing away from the first substrate. 6.The method of claim 1, wherein the bond pad comprises a first protrusionextending outward from a lower surface of the bond pad towards thesecond plurality of interconnect layers.
 7. A method of forming amulti-dimensional integrated chip, comprising: bonding a firstintegrated chip (IC) die to a second IC die along an interfacecomprising a dielectric and a conductive connector, wherein the secondIC die comprises a second plurality of interconnect layers disposedwithin a second dielectric structure on a second semiconductorsubstrate; etching the second IC die to form a recess defined bysidewalls of the second IC die; forming a bond pad within the recess,wherein a vertical line that is perpendicular to the interface extendsthrough the recess and the interface and is laterally separated from theconductive connector by a non-zero distance; forming a buffer layerwithin the recess; forming a masking layer over the buffer layer; andselectively etching the buffer layer and the second dielectric structureaccording to the masking layer to define trenches extending to thesecond plurality of interconnect layers, wherein the bond pad is formedwithin the trenches.
 8. The method of claim 7, wherein the recess isdefined by sidewalls of the second semiconductor substrate.
 9. Themethod of claim 7, further comprising: forming an array of image sensingelements within the second IC die.
 10. The method of claim 7, whereinthe conductive connector comprises: a first connector having a firstwidth and a second connector having a second width that is differentthan the first width.
 11. A method of forming a multi-dimensionalintegrated chip, comprising: forming a first connector along a top of afirst dielectric structure on a first substrate; forming a secondconnector along a top of a second dielectric structure on a secondsubstrate; bonding the first dielectric structure to the seconddielectric structure so that the first connector vertically contacts thesecond connector at an interface; and forming a bond pad laterally anddirectly between sidewalls of the second substrate, wherein the bond padis laterally outside of the first connector and the second connector andwherein the sidewalls of the second substrate vertically extend past atopmost surface of the bond pad.
 12. The method of claim 11, wherein thesecond connector is coupled to the bond pad by way of a second pluralityof interconnect layers disposed within the second dielectric structure.13. The method of claim 12, wherein the second plurality of interconnectlayers comprise a conductive routing layer having a bottommost surfacefacing the first substrate, wherein the conductive routing layercontinuously extends from directly below bond pad to laterally outsideof the bond pad and directly above the second connector.
 14. The methodof claim 12, further comprising: etching the second substrate to definean aperture extending through the second substrate; forming a bufferlayer within the aperture; forming a masking layer over the bufferlayer; and selectively etching the buffer layer and the seconddielectric structure according to the masking layer to define openingsexposing one of the second plurality of interconnect layers, wherein thebond pad is formed within the openings.
 15. The method of claim 14,further comprising: forming a dielectric layer over the bond pad andbetween sidewall of the bond pad; etching the dielectric layer to definea second opening that extends through the dielectric layer to expose thebond pad; and forming a metal within the second opening and on the bondpad.
 16. The method of claim 11, wherein the first dielectric structuresurrounds an interconnect layer having a topmost surface thatcontinuously extends from directly below the bond pad to directly belowthe first connector.
 17. The method of claim 11, wherein the firstdielectric structure surrounds a first plurality of interconnect layers;and wherein a topmost one of the first plurality of interconnect layershas a top surface that continuously extends laterally past opposingoutermost sidewalls of the bond pad and physically contacts the firstconnector.
 18. The method of claim 11, wherein the second dielectricstructure surrounds an interconnect having a horizontally extendingsurface that continuously extends from directly vertically above thefirst connector to laterally past an outermost sidewall of the firstconnector and directly vertically below the bond pad.
 19. The method ofclaim 7, wherein a bottommost surface of the conductive connectorcontinuously extends to opposing outermost sidewalls of the conductiveconnector; and wherein the vertical line is separated from thebottommost surface of the conductive connector by the non-zero distance.20. The method of claim 7, wherein the sidewalls of the second IC dievertically extend past an uppermost surface of the bond pad that facesaway from the first IC die.